This invention relates to a seat adjuster or track assembly for supporting a vehicle seat for selective back and forth adjustment in the passenger compartment of the vehicle.
Typically, the front seat of the vehicle is supported by two adjustable track assemblies, there being one track assembly beneath the seat along each side thereof. Each assembly comprises an upper track secured to the lower side of the seat and supported on a lower track to move back and forth in the passenger compartment. The lower track is anchored to the floor pan of the vehicle.
In the seat adjuster of the invention, a latch plate is fixed to and extends along the lower track of each assembly and is formed with a series of longitudinally spaced latching windows. A latch is pivotally supported on a mounting bracket on the upper track and includes at least one latching tooth which normally projects into one of the latching windows to lock the upper track against movement relative to the lower track. When the latch is pivoted on the mounting bracket to an unlatched position, the latching tooth is retracted out of the window to permit adjustment of the upper track and the seat carried thereby. In some cases, the latch may be formed with multiple longitudinally spaced latching teeth which extend into a plurality of adjacent latching windows.
In modern seat adjusters, a seat belt anchor is attached to the upper track, usually by means of a bracket, and serves as an anchor point for the fixed strap of a seat belt. As a result of anchoring the fixed strap of the seat belt to the upper track, the seat belt adjusts back and forth with the seat so as to increase the comfort of the passenger. When a frontal crash occurs, however, the load imposed by the passenger against the seat belt is transmitted to the upper track. Thus, the track assembly must be capable of sustaining heavier loads than is the case where the seat belt is anchored to a structure other than the track assembly.
During a frontal impact, the upper track of the assembly tends to move forward relative to the lower track. Such movement tends to cam the latch to its unlatched position. If the latch releases, the upper track becomes unrestrained against forward movement and increases the chances of passenger injury.